Hydraulic motors and driving systems employing same

ABSTRACT

An hydraulic motor comprises two, three or more rows of pistons and cylinders which rows are selectively drivable by fluid under pressure supplied to the motor to provide for different motor speeds for a given delivery of working fluid to the motor. Nonoperative rows of pistons may be retracted to reduce friction losses between the piston&#39;&#39;s followers and the cam track on which the followers react to rotate the motor rotor. A driving system employing the motor and a variable delivery fluid pump is also provided, the system thus having a plurality of speed ranges including high speed at low torque and low speed at high torque.

United States Patent [191 Foster et al.

[ Oct. 29, 1974 HYDRAULIC MOTORS AND DRIVING SYSTEMS EMPLOYING SAME [73] Assignee: Renold Limited, Manchester,

7 England [22] Filed: Dec. 8, 1972 211 App]. No.: 313,271

[30] Foreign Application Priority Data UNITED STATES PATENTS 5/1939 Alpern 91/492 3,006,148 10/196] Hause ..4l7/2l6 Primary Examiner-Edgar W. Geoghegan Assistant Examiner-William F. Woods Attorney, Agent, or Firm-Flynn & Frishauf 57 ABSTRACT An hydraulic motor comprises two, three or more rows of pistons and cylinders which rows are selectively drivable by fluid under pressure supplied to the motor to provide for different motor speeds for a given delivery of working fluid to the motor. Nonoperative rows of pistons may be retracted to reduce friction losses between the pistons followers and the cam track on which the followers react to rotate the motor rotor. A driving system employing the motor and a variable delivery fluid pump is also provided, the system thus having a plurality of speed ranges including high speed at low torque and low speed at high torque.

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Q B :m QR Qm 2m mQm 8m 9m 32 m 9m R DD HYDRAULIC MOTORS AND DRIVING SYSTEMS EMPLOYING SAME This invention relates to hydraulic motors, and to systems employing same.

This invention is related to those disclosed in copending US. Pat. application Ser. Nos. 313,271; 304,838; 304,840; and 304,748, all assigned to the same Assignee as the present application.

An object of the present invention is to provide an hydraulic motor having more than one speed for a given delivery of fluid under pressure to the motor.

A further object of the present invention is to provide a driving system including an hydraulic motor of the invention, having more than one speed range.

SUMMARY OF THE INVENTION The present invention broadly provides an hydraulic motor having a rotor comprising at least two rows of pistons and cylinders, and adjustable valve means for supplying fluid under pressure into the'cylinders and for allowing it to exhaust therefrom, thereby to drive the pistons and rotate the rotor, the valve means being adjustable to communicate a pressure fluid inlet and an exhaust fluid outlet of the motor with one or both of said rows of pistons and cylinders thereby to selectively .operate said rows of pistons and cylinders to provide for at least two different motor speeds for a given delivery of working fluid to the motor. v

When fluid under pressure is delivered to a lesser number of rows of pistons and cylinders, the motor runs at a higher speed but with a reduced torque output in each case where the delivery of working fluid to the motor remains the same.

The present invention also provides a driving system comprising a variable delivery pump connected to supply fluid under pressure to an hydraulic motor of the invention, and the motor and the pump may be connected in a closed loop hydraulic system including a booster pump to make up the system leakage.

Such a system has two speed ranges depending upon the setting of the valve means.

Preferably, the valve means is adjustable in response to a fluid pressure signal supplied to the motor to operate the motor at one of its two speeds of operation.

The valve means may be adjustable in response to a cessation of said fluid pressure signal supplied to the motor to operate the motor at the other of its two speeds, and in the absence of said fluid pressure signal the valve means may be adjustable by fluid under pressure supplied into said pressure fluid inlet to operate the motor at said other of its two speeds.

Alternatively, an hydraulic motor of this invention may comprise at least three rows of pistons and cylinders, in which case the valve means is adjustable to communicate the pressure fluid inlet and the exhaust fluid outlet respectively with one, two or three rows of pistons and cylinders to operate said one, two or three rows to provide for at least three different motor speeds for a given delivery of working fluid to the motor.

Thus, an hydraulic motor of this invention may have more than three rows of pistons and cylinders, the valve means being adjustable to communicate the pressure fluid inlet and the exhaust fluidputlet respectively with an increasing number of the rows of pistons and cylinders to operate them so as to provide for as many different motor speeds for a given delivery of working ders.

The valve means may be adjustable to connect the non-operative row or rows of pistons and cylinders with the exhaust fluid outlet.

This arrangement offers simplicity in a number of respects hereinafter detailed in relation to specific embodiments of hydraulic motor according to the invention. If the motor should be required to reverse however, by changing over the pressure fluid inlet and the exhaust fluid outlet, the inoperative row of pistons and cylinders communicating solely with the exhaust fluid outlet is subjected to inlet pressure in the higher speed setting or range. during reversal. Also, when the motor is used in a closed-loop hydraulic system including a booster pump to make up system leakage, the exhaust fluid outlet is always at a pressure above atmospheric pressure and therefore the non-operative row of pistons and cylinders pressurized in any event with consequent loss of torque.

In an alternative arrangement according to the invention therefore and in the case where the hydraulic I motor of the invention comprises two rows of said pissubject to the pressure in a further space within the motor casing.

Preferably also, the piston outer ends carry cam followers which normally engage a cam track at least in part bounding said further space, the followers being tethered to the pistons and the pistons being movable to the inner ends of the cylinders to withdraw the followers out of engagement with said track.

Thus the present invention still further provides a driving system comprising a main hydraulic pump connected in a closed-loop to supply fluid under pressure to an hydraulic motor as defined in the preceding paragraph and a booster pump connected to said loop to boost the inlet pressure to said main hydraulic pump, and to pressurize said further space when said other row of pistons and cylinders is non-operative.

In use, said further space may be subject to pressure above atmospheric pressure to drive the inoperative pistons to the inner ends of their cylinders.

-BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-section of a part of one embodiment of an hydraulic motor according to this invention;

FIG. 2 is a diagram of a part of one embodiment of a driving system according to this invention and incorporating the motor of FIG. 1',

FIG. 3 is a cross-section of a part of a further embodiment of an hydraulic motor according to this invention;

FIG. 4 is a cross-section on line 2-2 in FIG. 3;

FIG. 5 is a partial cross-section showing a detail of the construction of the motor shown in FIG. 3;

FIG. 6 is a diagram of a part of a further embodiment of a driving system according to this invention and incorporating the motor of FIGS. 3, 4 and 5;

further embodiment of an hydraulic motor according to this invention; and

FIG. 8 is a view corresponding to FIG. 1 of a still further embodiment of an hydraulic motor according to this invention.

FIG. 9 is a cross-section on line X X in FIG. showing an hydraulic motor.

FIG. 10 is a section on lines A-A and B-B in FIG. 9 on the two sides of the line C-Cin FIG. 10, respectively.

FIG. 11 illustrates a detail of construction of the hydraulic motor illustrated in FIGS. 9 and 10.

FIG. 12 is a cross-section through afurther hydraulic motor.

FIG. 13 is a section on lines Y-Y in FIG. 12 and shows a detail of construction of the motor shown in F 1G. 12. 7

FIG. 14 shows a modification of the motor shown in FIG. 12 and.

FIGS. and 16 show a further modification, FIG. l6 being a section on line M-M in FIG. 15.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS Referring to the accompanying drawings, the motor is generally as described below butwith exceptions which will be described later with reference to FIGS. l-8.

Referring to the accompanying drawings and first to FIGS. 9 to 11, the motor comprises a stationary casing comprising a cast hollow stationary casing part hereinafter referred to as the second casing part or pintle I, having formed therein, coaxial bores hereinafter referred to as the second and third bores or the bores 5 and 2 respectively, and a passageway 8 communicating an opening 9 with the bore 2 and, through the bore 2, with the bore 5. A further opening 14 communicates with the bore 5 to one side of bore 2. A cylindrical tube 3 is press-fitted at one end in the bore 2 and the other end of the tube is press-fitted in a bore 4a, hereinafter referred to as a first bore, in a first stationary part or valve block 4 of the motor casing in turn which is press-fitted in the bore 5.The valve block 4 is additionally locked in the bore 5 by a plug 6 screwed into the end of the bore '5. Thus, the plug 6 prevents displacement of the valve block 4 under the action of fluid pressure in the bore 5. The valve block 4 is axially located in relation to the bore 5 by the tube3 which abuts the valve block at its inner end and a shoulder 7 on the pintle at its outer end. Openings 10 in the wall of the tube 3 communicate a set of ports each formed by aligned openings 11 and 12 in the valve block4 and the pintle 1 respectively with the bore of the tube 3 and hence with the passageway 8 and the opening 9 to the outside of the motor casing.

The motor is assumed to run in the direction of arrow Z in FIG. 9 for the purposes of this present description, although the motor may be driven in the opposite direction. For the direction of rotation Z the opening 9 constitutes the inlet in the motor casing for the supply of fluid under pressure into the cylinders 51 of a rotatable assemblage of pistons and cylinders 60, 51 the fluid passing through the passageway 8, the bore of the tube 3 and ports 11, 12 into the cylinders 51. The opening 14 constitutes the exhaust outlet to the outside of the motor casing in communication with a further set of ports, each formed by an opening 15 in the pintle 1 and a passage 16 in the valve block 4 via an annular passage 13 defined between the outside of the tube 3 and the bore 5.

The radially outer ends of the openings 12 and 15 are arranged alternately and equi-spaced, in a ring on the diameter 18 of the pintle, with their centres lying in the plane X-X in FIGS. 10 and 11 normal to the axis of the tube 3 and the bore 5. FIG. 11 is a development of the interface between the tube 3 and the valve block 4. This shows that the openings 15 are offset axially of the bore 5 with respect to the openings 12 at their radially inner ends where they open to the interface. This is to allow sufficient spacing at 17 between the inner ends of the adjacent openings 12 and 15 to maintain a fluid proof seal between them by virtue of the press-fit of the tube 3 in the valve block 4.

At their outer ends adjacent openings 12 and 15 are sealed from each other by virtue of the press-fit of the valve block 4 in the bore 5.

The openings 12 and 15 communicate alternatively with the cylinders 51 through openings 20 in a porting ring 19 rotatable with the assemblage of pistons and cylinders, on the diameter 18 of the pintle l, and rotation of the assemblage of pistons and cylinders is effected by the action of the fluid under pressure supplied into and exhausted from the cylinders 51 through the openings 20 and the inlet and exhaust ports respectively.

The motor casing further comprises two identical half caps 22 and 25 formed as castings and located and attached to one another by dowels 28 and bolts 26. The half caps are in turn located and attached respectively, on opposite sides to the pintle 1, and a cast shaft sealretainer cap 36. Thus the half cap 22 is dowelled at 24 and bolted by bolts (not shown) to the pintle 1 at a spigot joint 23 incorporating an O-ring seal 40 in a groove 41 and the shaft seal-retainer cap 36 is dowelled and bolted to the half cap 25 at a spigot joint 37 incorporating an O-ring seal 38 in a groove 39.

Clamped between the half caps 22 and 25 is a cam disc 27. The dowels 28 and 24 ensure that the cam disc 27 is correctly orientated with respect to the inlet and outlet ports and therefore the proper operation of the motor.

Bores 29 and 32 of the half caps 22 and 25 mount taper roller bearings 31 and 34 for the rotor 42 which incorporates the cylinder block 50 of the assemblage of cylinders 51, and pistons 60 the bearings being located axially against shoulders 30 and 33 on the half caps and'by shims 47 and 48 on shoulders 43 and 44 on the cylinder block 50, the bearings being retained by nuts 45 and 46.

The cylinder block 50 extends outside the motor casing through the shaft seal-retainer cap 36 where it presents a driving boss constituting the driving shaft 142 of the motor. The cap 36 retains a shaft seal 49 which prevents the leakage of fluid between the cylinder block 50 and the casing.

The half cap 22 has a drain hole 74 threaded to receive a connection to the interior of the motor casing around the outside of the rotor 42. The half cap 22 has on the same pitch circle as the hole 74 a number of blind bolt holes 75 useful for fastening the motor to a supporting frame 76. The spigot diameter 73 presented exteriorly of the motor casing is useful for locating the motor with respect to such a frame.

The drain hole 74 in the identical half cap 25 lies at a different orientation to that in the half cap 22 with respect to the rotor axis, and the half cap 25 also has on the same pitch circle as the drain hole a number of bolt holes for alternatively fastening the motor to a frame.

This permits mounting of the motor, which may be done from either side, using the fastening bolt holes in the half cap 22 or 25, in various orientations, the drain hole 74 in the uppermost position being utilized and the other drain hole being blocked off;

Referring now to FIGS. 12 and 13, the stationary casing is generally as hereinbefore described with reference to FIGS. 9 and 10 and parts corresponding with parts already described are indicated by the same reference numeral suffixed with the letter a.

The pintle la has somewhat longer tube 3a and a somewhat longer tubular end portion presenting the diameter 18a. The valve block 4a is also elongated and has passages 16a to connect two sets of openings a with the passage 13a. Furthermore the diameter of the openings 11a is locally reduced (see FIG. 13) to maintain a sufficient sealing land 17a between the openings Ila and 16a at the interface between the tube 3a and the valve block 4a.

The porting ring 19a makes provision of holes 20a for serving an assemblage of two rows of .pistons and cylinders 51a, 60a.

Instead of adjacent bores in the two rows of cylinder bores being positioned side by side as shown in FIG. 12, they may be staggered as shown in FIG. 14. Such angular displacement of the two rows of cylinder boresrespectively is not detrimental and may improve the performance of the motor by smoothing the output torque.

FIGS. 15 and 16 show a modification in which instead of elongating the valve block 4 the bore 5 contains cast on portions 4b defining the ports 11a, 12a for the right hand row of pistons and cylinders and in part the first bore hereinbefore referred to. Thus the cast on portions engage the outer diameter of the tube 3:! directly in this case. The openings 16b defined in the wall of the part of the first bore formed in the pintle In between adjacent cast on portions 4b form part of a passage communicating the openings 15a for the right hand row of pistons and cylinders with the passage 13a and the passages 16 in the valve block 4 also with the passage 13a.

The identical construction of the two half caps 22 and 25 offers manufacturing economies and alternative mounting arrangements for the motor.

The construction of the pintle as a casting with a pressed in valve block permits the use of a standard casting for the pintle 1 or In irrespective of the number of cylinders per row of cylinders and therefore valving holes 12 and 15 or 120 and 15a in the pintle.

The motors described may be driven in the opposite direction by reversing the fluid connections to the openings 9 and 14. l

A valve sleeve 108 replaces the valve block 4a previously described. A linearly displaceable valve member or spool 102 has a land 1020 at one end which slides in the bore of the valve sleeve 108. At its opposite end the spool 102 slides in the bore ofthe tube 103 1 communicating fluid under pressure with the bore of the tube. The bore of the tube 101 opens into a first space 150 defined between one end face, the left hand end face in FIG. 1 of the spool 102, and the casing plug 6 previously described.

The spool 102 is displaceable from a first position shown in FIG. I, in which it is located against the plug 6, to a second position in which the land 1020 engages against the adjacent end of the tube 103. The ports formed by aligning openings in the tube 103, the valve sleeve 108 and the pintle lpreviously described are inclined so as to open to the bore of the tube 103 to one side of the spool 102 when the spool is in its first position.

The two rows of pistons and cylinders are of equal total cylinder capacity.

The motor will be assumed to operate with 9 as the fluid pressure inlet and 14 as the exhaust fluid outlet.

When the spool 102 is in its first position, as illustrated in (FIG. 5) the motor operates as previously de scribed with both rows of pistons and cylinders operative and working to drive the motor rotor.

To operate the motor in a single row mode a fluid pressure signal is supplied, equal to the inlet fluid pressure at 9, through the fitting 1016 (FIG. 5) to the bore of the tube 101 and then to the space 150. The spool 102 is, in consequence, displaced to its second position. The spool has a circumferential groove 4 which then interconnects all the inlet ports 105 to the left hand row of pistons and cylinders in FIG. 1 as well as the outlet ports from these pistons and cylinders with the annular passage 13a and the exhaust fluid outlet 14 via cut-outs 106 in the end of the tube 103 and slots 109 in the valve sleeve 108. The left hand row of pistons and cylinders is therefore rendered non-operative but fluid under pressure from the pressure fluid inlet 9 is still supplied to the right hand row of pistons and cylinders as previously described, to operate the motor.

The net flow of working fluid into and out of the cylinders in the left hand row is nil. Hence if working fluid is still supplied to the inlet 9 at the same rate, the motor runs at twice the speed and if the working fluid is still supplied at the same pressure, the torque output of the motor will be approximately one half of what it was with the spool 102 in its first position and the motor running in its double row mode.

The bore of the tube 101 is normally connected through the fitting 1010 with the exhaust fluid outlet 14. Under this condition the inlet pressure in the bore of the tube 103 acts on the right hand end face in FIG. 1 of the spool which is of lesser effective area than its left hand end face in this figure, to maintain the spool in its first position and to return it to its first position when the bore of the tube l0l is reconnected with the exhaust fluid outlet to change over the operation of the motor from the single row" mode to the double row" mode.

Four slots 109 are provided in the valve sleeve 108 to communicate the exhaust ports with the exhaust fluid outlet.

The land 1026 carries an O-ring seal 111 in a groove in the land to prevent leakage of pressure fluid escaping past the land and to increase the machining tolerances affecting the concentricity of the spool 102 and the .bores of tube 103 and sleeve 108.

outlet via the non-return valve 158 or 159. No flow occurs through the non-return valve 159 unless the flow in the closed-loop system is reversed, on overrun of the motor for example.

The conduit 155 communicates also with a manual or solenoid operated, two position selector valve S. In its right hand diagrammatically illustrated position (1) the valve S communicates the conduit 155 with the conduit 101d and thus with the bore of the tube 101. The motor then operates in the double-row mode. In its diagrammatically illustrated position (2) the valve S communicates the conduit 101d with the pressure fluid inlet 9 via the conduit 154 and a conduit 160. A fluid pressure signal is therefore supplied to the motor and the motor then operates in its single-row mode. In the event of overrun a non-return valve 162 in the conduit 160 prevents the spool 102 returning to its first position.

The driving system described with reference to FIG. 2 is suitable for transmitting drive to a driving wheel of a vehicle such as a fork lift truck or an optionally offhighway vehicle. In the double-row mode the motor produces high torque at low speed for operating in a loaded condition or on rough terrain and in the singlerow mode the motor produces low torque at high speed for travelling, on the level, or surfaced roads.

With the system described the pistons of the left hand row of pistons are maintained in following relation with the cam during single-row operation and some additional drag and frictional losses therefore result during over run or if the motor is reversed since the pistons and cylinders of the inoperative row are then subject to high pressure. However, the system offers the compensating advantage of simplicity particularly where the motor is not required to operate or operate unduly in reverse.

Referring now to FIGS. 3, 4 and 5 the motor is, in this case, again as described in co-pending application Ser. Nos.304,838; 304,840; and 304,748 and withparticular reference to FIGS. 7 and 8 of application Ser. No. 304,840 but with the following exceptions which will alone be described if they have not already been described herein with reference to FIG. 1.

A sliding cup 117 has recesses 118 connecting the outlet ports 119 of the left hand row of pistons and cylinders with the annular space 13a which in turn connects with the exhaust fluid outlet 14. The cup 117 has holes 121 connecting the inlet ports 12a with the bore of the tube 122 which corresponds with the tube 103 previously described with reference to FIG. 1. The cup 117 slides on the outer diameter of the tube 122.

The cup has a boss co-axially press-fitted in a bore in the floor of the cup and the boss has a central bore which slidably receives the tube 101. At its outer periphery the boss has a keyway 124 which receives a tab 123 formed by bending inwardly a portion of the wall of the tube 122 disposed between slots. The tab 123 co-operates with the keyway 124 to prevent rotation of the cup.

The cup 117 is shown in its first position corresponding with double-row operation of the motor, and is displaceable to a second position correspondingwith single-row operation of the motor by a fluid pressure signal supplied along the tube 101 as hereinbefore described. In its second position the cup engages the adjacent end of the tube 122.

The cup has a circumferential groove 126 at its outer diameter defining with the motor casing a second space which interconnects all the inlet and outlet ports 12a and 119 of the left hand row of pistons and cylinders when the cup is in its second position. The groove 126 is connected with a space 129 between the pintle 1a and the cylinder block 500 which forms the motor rotor, via two sets of drillings 127 and 128 in the pintle, the drillings 127 being plugged at their outer ends with plugs 131 (see FIG. 4).

The porting ring 19a previously described has lengthwise extending grooves 132 in its outer diameter which communicate the space 129 with a space 12% at the opposite end of the porting ring and this space is vented to atmosphere via a drain fitting (see FIG. 5) on the outside of the motor casing.

The space 100 is, in this embodiment, sealed off from the space 12% by a seal 134.

The cup 117 has O-ring seals in grooves at 117a and I17b respectively.

Referring now to FIG. 6, corresponding parts are indicated by the same references as used herein with reference to FIGS. 2, 3, 4 and 5.

The selector valve 5 has two positions (1) and (2) representing the double and single row modes of operation of the motor, as before.

Non-return valves 164 and 165 connected between the conduits 153 and 154 respectively select the conduit at inlet fluid pressure, which is then communicated with the conduit 101a via the selector valve S to cause the motor to operate in its single-row mode. The boost pressure from the pump B is at the same time connected via a conduit 166, a boost pressure relief valve 203, the selector valve 8, and a conduit 167 with the space 100 in the motor casing, and the fluid flow returns to tank T via a restriction 206, a non-return pressure relief valve 204 in parallel with the restriction, and a conduit 168. Thus the pressure in the space 100 is determined by the blow-off pressure of the valve 204 when the motor is operating in the single-row mode.

The restrictor 206 is selected such that inthe doublerow mode of operation of the motor (S, position (1)), the case leakage from space 100 can flow through the conduit 167, the restrictor 206 and the conduit 168 without any significant build-up of pressure in the space 100. In the single-row mode, the booster pump excess flow is however, arranged to be sufficiently larger than the case leakage flow so that blow-off occurs through the valve 204 and a pressure in excess of atmospheric pressure is generated in the space 100 just sufficient to force back the pistons of the left hand row of pistons and cylinders to the inner end of their cylinder bores so that the roller followers 63 which are tethered to their pistons are withdrawn out of engagement with their cam disc 27. When this occurs, of course, the inoperative pistons and cylinders in the single-row mode of operation of the motor are subject only to atmospheric pressure in the space 129, 129b, through which the fluid in the cylinders is ejected to tank T so that a pressure only slightly above atmospheric pressure is required in the space 100 to overcome the centrifugal forces acting on the pistons and the tank T pressure.

The roller followers 63 are mounted in through bores in the pistons which subtend an angle greater than 180 whereby the roller followers are tethered to the pistons. The roller followers are located axially by wire rings 64, 65 extending circumferentially of, and held in grooves in, the cylinder block 50a. Instead of the wire rings 64, 65, rings mounted on, or formed as part of the motor casing may be used to locate the roller followers axially.

In the double-row mode of operation the fluid flow from the relief valve 203 is passed by the selector valve S, via the conduit 168 directly to the tank T.

As before, the selector valve S, may be manually or solenoid operated.

The non-return valves 164, 165 may be replaced by a single non-return valve 207 communicating the conduit 101d with the conduit 154 if single-row operation is required only for forward drive. t

The selector valve 8,, or for that matter the selector valve S could equally be a spool valve or a rotary valve or a sliding face valve or any other type of valve, or again, a combination of valves to perform the same function as has been described for the selector valve S, or the selector valve S.

The left hand end section of the selector valve S could be omitted and the valve 203 connected permanently to the conduit 167. The restriction 206 could also be omitted so that the conduit 167 is connected to the conduit 168 only via the valve 204. In this case the space 100 is permanently pressurized sufficiently to force back the non-operative pistons in their cylinders to ensure their free wheeling.

The selector valve S or a combination of valves replacing the selector valve S, and performing the same function as the selector valve 8, could be designed to restrict the flow into conduit 101d so that the cup 117 moves slowly when moving from its first position to its second position. This allows the left hand row of pistons and cylinders to be cut off relatively slowly whilst allowing a temporary progressively reducing leakage past the selector valve and cup 117. This cushions the step capacity change of the motor and allows-the pump flow and the motor output shaft speed to be more easily resynchronised to the changed mode of operation of the motor.

The pump P may be a variable delivery pump whereby the motor M may be operated in two speed ranges depending upon the setting of the selector valve 5,. Since the roller followers are withdrawn from contact with the cam disc in the single-row mode of operation friction losses are reduced. There is no transfer of fluid between the cylinders of the inoperative row of pistons and cylinders. Flow losses are therefore also reduced. The motor may be operated in either mode and in either direction under these conditions.

FIG. 7 shows a modification of the motor described with reference to FIGS. 3, 4 and 5 where the cup 117a replaces the valve block 4a in FIG. 12 described hereinabove. Elongated openings 117b communicate the 5 inlet ports of the right hand row of pistons and cylinders with the bore of the tube regardless of the position of the cup. Slots 117c in the cup communicate the exhaust ports of the right hand row of pistons and cylinders with the space 130 regardless of the position of the cup. The motor is otherwise as described with reference to FIGS. 3, 4, and 5.

FIG. 8 shows a motor generally as described with reference to FIG. 1 of the specification except that it is extended to four rows of pistons and cylinders instead of two and each row of pistons and cylinders is as described with reference to FIG. 1 of this specification. Parts corresponding with parts previously described and which it is necessary to refer to again in describing the present embodiment will be referred to by the same reference numeral with the suffix d added. However, 'only the departures in construction from that previously described with reference to FIG. 1 of this specification will now be described in detail and these involve the valve means for supplying fluid under pressure into the cylinders and for allowing it to exhaust therefrom.

In FIG. 8 the valve sleeve 108d and the tube 103d together present four sets of inlet and outlet ports, one set for each of the four rows of pistons and cylinders.

The motor will again be assumed to operate with 9d as the fluid pressure inlet and 14d as the fluid pressure outlet, although these connections can be reversed in order to reverse the motor.

Thus one of the inlet ports 105d to the first row of pistons and cylinders is indicated, and corresponding inlet ports 300, 301 and 302 are also indicated for the second, third and fourth rows of pistons and cylinders respectively, proceeding from left to right in the drawmg.

The valve member or spool 102d has a central longitudinal bore which slidably receives a central control rod 303 which passes co-axially through the tube 103d, the rod 303 being supported towards its left hand end in the bore of the spool 102d and a co-axial bore in the casing plug 6d and towards its opposite end in a bore in the motor casing proper through which the rod can slide so as to be adjustable lengthwise, from outside the motor casing, with respect to the spool 102d and the plug 6d. Suitable packing glands 304 and 305 are provided in the casing and plug respectively to prevent the leakage of pressure fluid along the rod 303.

The rod 303 has an axial drilling or bore 306 which communicates with a radial drilling or bore 307 which normally opens into a first space 150d. The circumferential groove 4d defines a second space between the spool 102d and the motor casing sleeve 1080' which communicates with the space 150d through a radial drilling or bore 308 and a stepped axial drilling or bore 309 in the spool 102d having an orifice 310 at its mouth. The drilling 309 houses a first spring-pressed non-return ball valve means 311 which seats on the drilling step.

The high pressure space in the bore of the tube 103d communicates with the space 150d through a stepped axial drilling 312 having an orifice 313 at its mouth. The orifice 313 is identical with the orifice 310. The drilling 312 houses a second spring-pressed non-return ball valve means 314. High pressure fluid in the space 150d is prevented from escaping into the groove 4d by the non-return valve 311.

If the motor is reversed, high pressure fluid from the groove 4d enters the space 150d and is prevented from escaping into the bore of the tube 103d by the nonreturn valve 314. Thus the space 150d is always at high pressure regardless of the direction of rotation of the motor and the high pressure acts on the left hand end face of the spool 102d exposed in this space.

The drillings 306 and 307 communicate the space 150d with the motor casing 100a through a passage 315 and the casing 100d is vented to tank through a case drain (not shown). High pressure fluid from the space 150d can therefore leak to the casing through the drillings 306 and 307 so long as the mouth of the drilling 307 is uncovered by the edge 316 of the central longitudinal bore in the valve spool 102d where it opens into the space 150d, and the extent of this leakage is determined by the area of the mouth of the drilling 307 which is uncovered by this metering edge 316.

The mouth of the drilling 307 has an effective area compared with the orifices 313 and 310 such that when the drilling 307 is fully uncovered in the space 150d the pressure of fluid in the space approaches that of the casing 100d and the valve spool 102d, which is linearly displaceable, is urged to the left in FIG. 8 either by high pressure fluid in the bore of the tube 103d acting on the opposite right hand end face of the spool or by high pressure fluid in the differential area between the groove 4d acting on the right hand face of the land 102cd and the left hand face of the right hand land of spool 102d. Both these faces are of lesser surface area than the left hand end face of the spool 102d exposed in the space 150d. When the metering edge 316 fully covers the mouth of the drilling 307 the pressure of fluid in the space 150d rises to the inlet pressure and the valve spool 102d is urged to the right in the drawing by the pressure of fluid in the space 150d, acting on the full left hand end face of the spool. At intermediate positions of the metering edge 316 relative to the mouth of the drilling 307, intermediate pressures are set-up in the space 150d between inlet pressure and that of the casing 100d and the metering edge 316 on the valve spool 102d will therefore always move to an equilibrium position relative to the drilling 307 in which the fluid pressure forces acting on the valve spool are balanced. The position of the rod 303 therefore always determines the position of the valve spool between its extreme left and right hand positions in which the land 102cd engages respectively against the plug 6d and the left hand end of the tube 103d, the spool followingup" the movement of the rod in either direction between these two positions, until it reaches an equilibrium position.

The groove 4d in the present example is long enough to isolate up to three of the rows of pistons and cylinders, that is to say the rows served by the ports 105d, 300 and 301. When isolated by the groove 4d both the inlet ports and outlet ports 350 or 351 or 352 or 353 of a row of cylinders are communicated with the exhaust fluid outlet 14d via the cut outs 106d and the slots 109d.

Movement of the rod 303 to the right in the drawing therefore will cause the valve spool 102d to move to the right to isolate either the first or the first and second or the first, second and third rows of pistons and cylinders, thereby to increase the speed of the motor in steps for a given delivery of fluid under pressure to the fluid pressure inlet of the motor.

A circlip 330 on the rod 303 prevents the mouth of the drilling 307 being closed off in the plug 6d.

The rod 303 mayconveniently be positioned in the preset positions necessary to operate the motor with one, two, three or four rows of the pistons and cylinders by means of spring pressed detents engaging in depressions in the surface of the rod.

The motor as described with reference to FIG. 8 may also be connected in a fluid circuit to be driven by a variable delivery fluid pump. in this case a driving system is provided having four speed ranges.

It will be evident that the valve means described with reference to FIG. 8, and the servo arrangement for operating it, may be extended to control the operation of up to more than four rows of pistons and cylinders in an hydraulic motor generally as described. Alternatively, it may be used to control the operation of just two rows of pistons and cylinders instead of the valve means as described with reference to FIG. 1 of this specification.

The hydraulic motors which have been described are generally of a known kind comprising an assemblage of rotatable pistons and cylinders, to provide the output drive of the motor, by the action of fluid under pressure supplied into and exhausted from the cylinders through a ring or rings of inlet and exhaust ports in a stationary part of the motor casing, such as have been described. The invention is applied to hydraulic motors of this kind, to provide for at least two different motor speeds for a given delivery of working fluid to the motor, in a manner illustrated in the specific embodiments described with reference to the accompanying drawings.

A motor according to the invention operates as a pump, on overrun in a closed circuit transmission, and may be used purely as a pump. The invention accordingly includes pumps as well as motors.

The rows of pistons and cylinders are not necessarily of equal total cylinder capacity as has been described or illustrated.

We claim:

1. An hydraulic motor having:

a rotor comprising a plurality of rows of pistons and cylinders;

adjustable valve means for supplying fluid under pressure into the cylinders and for allowing the fluid to exhaust therefrom, thereby to drive the pistons and rotate the rotor, the valve means comprising a linearly displaceable valve member having a central longitudinal bore therein and which is selectively adjustable to communicate a pressure fluid inlet and an exhaust fluid outlet of the motor with different numbers of said rows of pistons and cylinders to provide for at least two different motor speeds for a given delivery of working fluid to the motor; control rod slideably received in said longitudinal bore and adjustable lengthwise with respect to the valve member and the motor casing, the control rod extending outside the motor casing at one end and extending through a first space defined between one end face of the valve memberand the casing towards its other end; and

a non-return valve means communicating said space with said fluid pressure inlet;

the control rod having a radial bore presenting a cate the pressure fluid inlet and the exhaust fluid outlet mouth the effective uncovered area of which, open respectively with an increasing number of the rows of to said space is controlled by said valve member, pistons and cylinders to operate them so as to provide said radial bore communicating said space with a for as many different motor speeds for a given delivery pressure fluid zone at a pressure lower than the of working fluid to the motor as there are rows of pispressure of fluid in said fluid pressure inlet for the tons and cylinders. leakage of fluid from said first space at a rate 4. An hydraulic motor as claimed in claim 1 wherein I greater than it is supplied through said non-return the Valve means is j sta to Connect the nonvalve means, said valve member being subject to operative row or rows of pistons and cylinders with the Y the pressure'of fluid in said inlet on a face opposite n exhaust fluid Ouflfit.

to said one end face of the valve memb r f l r 5. An hydraulic motor as claimed in claim 4 wherein area than said one end face, the valve memb f l. said valve member defines with the motor casing 21 seclowing-up movements of the control rod selectively 0nd Space in Permammt communiCatiOn with Said r communicate id pressure fl id i d id haust fluid outlet for one direction of rotation of the exhaust fluid outlet with said different numbers of 15 motor, P Said Second Space is brought into Communiid rows f pistons d li d as h valve cation with inlet and outlet ports of an increasing nummember moves i one di i to f ll moveber of said rows of pistons and cylinders as the valve m f id m r d member is displaced by fluid under pressure acting in said first said space thereby to render those rows of pistons and cylinders inoperative.

6. An hydraulic motor as claimed in claim 5, wherein the motor is adapted to be reversed by reversing said 2. An hydraulic motor as claimed in claim 1 comprising at least three rows of pistons and cylinders, and wherein the valve means is adjustable to communicate the pressure fluid inlet and the exhaust fluidoutlet re- Spectivey with one two or three rows of pistons and pressurefluid inlet and exhaust fluid outlet, said second cylinders m operate Said one, two or three rows to space IS in communication with said first space through vide for at least three different motor speeds for a give a Second means and the of lea]? delivery of working fluid to the moton age of fluid from said first space through said bore 1s 3. An hydraulic motor as claimed in claim.1, wherein ond s ace to said first s ace throu h sai s ond more than three rows of pistons and cylinders 15 prop p g d ec return valve means when the motor is reversed.

vided and the valve means is adjustable to communigreater than the rate of leakage of fluid from said sec-, 

1. An hydraulic motor having: a rotor comprising a plurality of rows of pistons and cylinders; adjustable valve means for supplying fluid under pressure into the cylinders and for allowing the fluid to exhaust therefrom, thereby to drive the pistons and rotate the rotor, the valve means comprising a linearly displaceable valve member having a central longitudinal bore therein and which is selectively adjustable to communicate a pressure fluid inlet and an exhaust fluid outlet of the motor with different numbers of said rows of pistons and cylinders to provide for at least two different motor speeds for a given delivery of working fluid to the motor; a control rod slideably received in said longitudinal bore and adjustable lengthwise with respect to the valve member and the motor casing, the control rod extending outside the motor casing at one end and extending through a first space defined between one end face of the valve member and the casing towards its other end; and a non-return valve means communicating said space with said fluid pressure inlet; the control rod having a radial bore presenting a mouth the effective uncovered area of which, open to said space is controlled by said valve member, said radial bore communicating said space with a pressure fluid zone at a pressure lower than the pressure of fluid in said fluid pressure inlet for the leakage of fluid from said first space at a rate greater than it is supplied through said non-return valve means, said valve member being subject to the pressure of fluid in said inlet on a face opposite to said one end face of the valve member of lesser area than said one end face, the valve member followingup movements of the control rod selectively to communicate said pressure fluid inlet and said exhaust fluid outlet with said different numbers of said rows of pistons and cylinders as the valve member moves in one direction to follow-up movements of said control rod.
 2. An hydraulic motor as claimed in claim 1 comprising at least three rows of pistons and cylinders, and wherein the valve means is adjustable to communicate the pressure fluid inlet and the exhaust fluid outlet respectively with one, two or three rows of pistons and cylinders to operate said one, two or three rows to provide for at least three different motor speeds for a given delivery of working fluid to the motor.
 3. An hydraulic motor as claimed in claim 1, wherein more than three rows of pistons and cylinders is provided and the valve means is adjustable to communicate the pressure fluid inlet and the exhaust fluid outlet respectively with an increasing number of the rows of pistons and cylinders to operate them so as to provide for as many different motor speeds for a given delivery of working fluid to the motor as there are rows of pistons and cylinders.
 4. An hydraulic motor as claimed in claim 1 wherein the valve means is adjustable to connect the non-operative row or rows of pistons and cylinders with the exhaust fluid outlet.
 5. An hydraulic motor as claimed in claim 4 wherein said valve member defines with the motor casing a second space in permanent communication with said exhaust fluid outlet for one direction of rotation of the motor, and said second space is brought into communication with inlet and outlet ports of an increasing number of said rows of pistons and cylinders as the valve member is displaced by fluid under pressure acting in said first said space thereby to render those rows of pistons and cylinders inoperative.
 6. An hydraulic motor as claimed in claim 5, wherein the motor is adapted to be reversed by reversing said pressure fluid inlet and exhaust fluid outlet, said second space is in communication with said first space through a second non-return valve means, and The rate of leakage of fluid from said first space through said bore is greater than the rate of leakage of fluid from said second space to said first space through said second non-return valve means when the motor is reversed. 